The content of a digital image may have considerable impact on the compression of the digital image, both in terms of compression efficiency and compression artifacts. Pictorial regions in an image may not be efficiently compressed using compression algorithms designed and optimized for the compression of text. Similarly, text images may not be efficiently compressed using compression algorithms that are designed and optimized for pictorial content. Not only can the compression efficiency suffer when a compression algorithm designed for one type of image content is used on a different type of image content, but the decoded image may exhibit annoying compression artifacts.
Additionally, image enhancement algorithms designed to sharpen text, if applied to pictorial image content, may produce visually annoying artifacts in some areas of the pictorial content. In particular, areas in a pictorial region containing strong edges similar to text may be sharpened producing a visually displeasing image. While smoothing operations may enhance a natural image, the smoothing of text regions is seldom desirable.
The detection of regions of a particular content type in a digital image may improve compression efficiency, reduce compression artifacts, and improve image quality when used in conjunction with a compression algorithm or image enhancement algorithm designed for the particular type of content.